<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        body {
            background-color: #000;
            padding: 100px;
        }

        .btn {
            position: relative;
            width: 120px;
            height: 40px;
            color: rgb(68, 133, 218);
            font-size: 18px;
            line-height: 40px;
            text-align: center;
            overflow: hidden;
            border-radius: 5px;
            cursor: pointer;
            transition: all .2s linear;
        }

        .btn:hover {
            color: orange;
            transform: scale(0.9);
        }

        .btn:hover.btn::before {
            background-color: orange;

        }

        .btn::before {
            content: "";
            position: absolute;
            top: 50%;
            left: 50%;
            width: 200%;
            height: 200%;
            background-color: rgb(67, 130, 202);
            z-index: -2;
            transform-origin: left top;
            animation: rotate 3s linear infinite;
        }

        .btn::after {
            content: "";
            position: absolute;
            top: var(--w);
            left: var(--w);
            --w: 2px;
            width: calc(100% - 2* var(--w));
            height: calc(100% - 2* var(--w));
            background-color: rgb(0, 0, 0);
            z-index: -1;
            border-radius: 5px;
        }

        @keyframes rotate {
            to {
                transform: rotate(360deg);
            }
        }
    </style>
</head>

<body>
    <div class="btn">登录</div>
</body>

</html>